Various systems have been developed to measure differential signals from a device under test (DUT). There are a variety of ways to connect the test system to the DUT. These may include a soldered connection, RF connector, pressure contacts, wires/leads, pins, adapters, interposers, clip-ons etc. A common interface to connect the test system to the DUT is accomplished by using a pair of pins/short wires that are soldered to the differential test points, which are then connected to the test system. The problem with such systems is that ambient electric fields may interact with the exposed leads/pins, which lack shielding, injecting interference into the signals being measured. Interference injected into both leads/pins is referred to as common mode interference. The exposed leads/pins may experience both common mode interference and interference affecting the individual leads/pins. There is no mechanism to isolate the differential signal from these interferences at the exposed leads/pins, resulting in added signal noise that is measured by the testing system but is not present in the actual DUT's differential signal. Further, maintaining a uniform controlled impedance of these differential leads/pins supports repeatable measurements without degradation in the frequency response. However, real exposed leads/pins may bend and change position significantly during the testing process. Bending the exposed leads changes the corresponding impedances of the differential pair. Such uncontrolled impedances alter the frequency response of the signal at the testing system, leading to bandwidth loss and ripple currents. As such, the exposed leads reduce the accuracy of test measurements taken by a testing system, particularly when measuring a differential signal with higher frequency content.
Embodiments of the invention address these and other issues in the prior art.